In the preparation of many different foods--from dairy snacks to candies--it is necessary to be able to accurately measure out a quantity of a viscous or pasty foodstuff and charge it into a respective receptacle. This dosing operation must be carried out rapidly and automatically, with no variation in amount from dose to dose, and with no dripping or dribbling between doses.
Accordingly German patent No. 2,134,207 describes a pump-type system having a pair of tubes telescoping along a common vertical axis. The lower tube carries at its lower end a nozzle and the upper tube is supplied at its upper end with the liquid foodstuff to be dosed. Complex valve arrangements in the passage defined by the two tubes permit flow therein only downward from the nozzle and from the upper tube along the passage into the lower tube. Thus as the two tubes are pulled apart to increase the volume of the passage the nozzle check valve closes and the upper-tube check valve opens so the passage fills with the foodstuff, and when the tubes are pushed together to decrease the passage volume the upper-tube check valve closes and the nozzle check valve open so the passage empties through the nozzle.
This system is a fairly complex mechanism. Cleaning it is therefore quite difficult. When the device is used with a spoilable foodstuff it must be thoroughly cleaned frequently, so the operation costs for the apparatus are considerable.